NHC-catalyzed enantioselective C2-functionalization of 3-hydroxychromenones via α,β-unsaturated acyl azoliums.

A novel synthetic method for enantioselective C2-functionalization of 3-hydroxychromenones promoted by N-heterocyclic carbenes via the formation of α,β-unsaturated acyl azolium intermediates, which occurs with Coates-Claisen rearrangement is established. This synthetic strategy enabled the rapid assembly of enantiomerically enriched δ-hydroxychromenone-derived esters/amides under mild conditions with good to excellent yields and broad substrate scope.